Subscriber-controlled switching apparatus for telephone-exchange systems.



I v J. ERIOKSON. SUBSCRIBER CONTROLLED SWITCHING APPARATUS FOR TELEPHONE EXCHANGE SYSTEMS.

APPLICATION FILED NOV.12, 1906.

Patented Mar. 30, 1915.

a MEETS-SHEET 1.

J. ERIOKSON.

SUBSCRIBER CONTROLLED SWITCHING APPARATUS FOR TELEPHONE EXCHANGE SYSTEMS. APPLICATION EILED NOV. 12, 1906.

Patented Mar. 30, 1915.

3SHEETS-SHEET Z.

J. ERIGKSONQ SUBSCRIBER CONTROLLED SWITCHING APPARATUS FOR TELEPHONE EXCHANGE SYSTEMS.

' APPLICATION FILED NOV. 12. 1906.

' Patented. Mar. 30, 1915.

3 SHEETS-SHEET "IFIAQQL J'DIIN ERIGKSON, 01E CHICAGO, ILLINOIS, TRUST .AND SAVINGS BANK,

SUBSCRIBEBPCONTROLLEJD S-WITCHING APPARATUS EQfi ASSIGNOR, BY ME$N E ASSIGNMENCFS, It Film TRUSTEE, OF CHICAGO, ILLINOIS.

ra s m-Newest sirs'rnin's.

I,Ill33,373.

Application filed November 12, 1906. Serial No. 343,043.

To all whom it may concern:

Be it known that I, JOHN ERioKsoN, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful linprovenient in Subscriber-Controlled Switching Apparatus for Telephone Exchange Systems, of which the following is a specification.

M y invention relates to automatic or semiautomatic telephone exchange systems in which the subscribers are provided with impulse-transmitting mechanisms or calling devices for controlling the operations of the electrically propelled and step by stepactuated switches at the exchange or central station.

in certain respects my invention is in the nature of an improvement on the system disclosed in application Serial No. 278,901. In said prior application the subscribers calling dial is adapted bv its forward rotation to operate a subscribers individual switch, and by its back rotation to then operate the next or succeeding switch, such, for example, as a first-selector, and with this arrangement the initial or first vertical step of the selectors and connectors is also accomplished by the forward rotation of the dial.

present invention now contemplates the operation of the subscribers individual switch ,by the forward rotation of the subscril'iers dial or calling device, but over the rotary side of the subscrihers line instead of over the vertical side thereof, which latter is the case in said former application, where by all selectors and connectors or other automatic switches are controlled or operated entirely by theback rotation of the subscribers dials or calling devices, the subscribers individual switches thus constitutmg the only devices which are operatively responsive to the forward 'rotation of said dials or calling devices.

\Vith such improved arrangement and mode of o 'wration l find that better results" are obtained and that greater certainty of actioii sinsured on the part of the exchange apparatus- To the foregoing and other useful ends, my invention consists in certain features of improvement and details of construction Specification of Letters Patent.

Patented Mar. 318, IFIE.

and combinations and circuit arrangements hereinafter described and claimed.

In the accompanying drawings, F1 gure 1' is a rear elevation of the subscribers telephone switching mechanism embodying the. principles of my invention, showing the easing removed. Fig. 2 is a similar elevation showing a number of the parts removed to shows the relation of the impulse springs and the controlling impulse wheel in normal position. Figs. 5, 6 and 7 show the relative positions of the parts in Fig. 4 when the dial is carried forward. Figs. 8 and 9;v

show the relative positions of the same parts as the dial returns to normal position. Fig. 10 is a diagrammatic view showing in a sim ple manner the relation of the most essential parts in the telephone and the connecting circuits with the line conductors. Fig.

11 is a diagram showing an established connection from the calling subseribers station through an individual switch and a firstselector and a connector to the called subscribers line. Fig. 12 is a plan view of a se line switch, showing the relative position of the different magnets.

In detail the subscriber mechanism, or socalled keyboard comprises two parallel and similar plates 2 held together by suitable tie-rods 3 capped with screws 4. Perpe" c-ilarly, and through. the center of said plates 2, there passes a shaft 5 suitably journaled and adapted to rotate. At the outer end of said shaft there is rigidly secured a dial 6 with a suitable number of finger-holes 7, properly numbered, by means of which the subscriber is guided in send ing the proper number of impulses over the line. there is a locking dog 8 which, in combination with, the locking cam 9 that is suitably pivoted to the rearmost one of the parallel plates 2, furnishes the means for lockin the dial (3 when the telephone is in norma 100 position-that is, when the receiver 10, shown in Fig. 10, is placed on the switchliook 11. The switch-hook carries a cam 12 (Fig. 1), which latter is provided with Rigidly connected to the shaft bar a finger'1j3 upon the extremity of which there is a, aterally projecting insulating member 14which, when the switch-hook .is raised, engages the thumb-like section 15 of the locking cain 9, retaining said cam raised beyond the reach of the screw 16 of the locking dog 8, which screw projects to the rear so that the dial may be freely rotated while the switch-hook is up. When the switch-hook is down the insulating member 14 is, of course, withdrawn from the locking cam 9, the frontpart of which latterfalls within the radius of the rotation of the screw 16 for preventing rotation of the dial, as already explained. It will be noticed that the locking cam 9, furthermore, is provided with an insulating cap 17 that works in conjunction with the so-called ground spring 18, retaining the latter at certain times away from the ground post 19. As soon as the dial is rotated, however, the screw 16, which passes under the looking cam 9, strikes the heel 20 of the latter, driving the insulating member 17 to the rear of the angled section 21 of the ground spring 18, permitting the latter to engage the ground spring 19, thus establishing the ground spring circuit. But when the receiver is restored to the hook, as shown in Fig. 10, the insulating member 14: passes into engagementwith the ground spring 18, driving the latter outwardly sufficiently to permit the tip 17 of the locking cam 9 to clear the angled section 21, at which time the locking cam 9 falls into its normal locking position. The cam 12 is further provided with members 22 and 23, the for mer for controlling the release springs 24, 25 and 26, and the latter for controlling the ringer circuit spring 27 as well as the primary circuit springs 29 and 30 and the secondary circuit springs 28 and 28.

It will be noticed that the locking cam 9 is provided with a restoring spring 30 which insures the drop of the said cam to normal position when the switch-hook is depressed. The switch-hook proper is made up of two sections a and b, the former being insulated from the latter to prevent the subscriber from being electrically shocked upon handling the section a. Both sections are suitably connected by screws or securing means 31. The section b is bifurcated, the prong 32 being pivoted at 33 to the front frame plate of the mechanism or so-called keyboard, and the prong 34 being pivoted at 33 to the back plate of said keyboard. The prong 32 extends rearwardly, as shown in Figs. 1 and 2, and is provided at its ter: minal with a ratchet 35 controlled by a retracting spring 36, which ratchet is adapted to engage the ratchet-wheel 37 whenever the switch-hook is pulled down. Normally the said ratchet 35 is retained out of engagement with the said ratchet-wheel 37 by a rest 38; but as the switch-hook begins to descend the prong 32 rises, and the under edge of the lateral member 35 of the ratchet engages the teeth of the ratchet-wheel 37, rotating the latter. This ratchet-wheel, as more clearly shown in Fig. 2, is in gear with a shaft 39, to which latter is secured the governor 40 for regulating the speed of the gear 37, and for regulating the downward movement of the switch-hook 11, in order to insure a contact of suilieient duration of the release springs 24, 25 and 26. The said gear-wheel 37 is loosely carried on the shaft 5, and is also adapted to be engaged by a second and similar ratchet -11 carried on the so-called impulse wheel 42, which latter is rigidly secured to the shaft 5. The said impulse-wheel is equipped with a set of so called impulse teeth 13 which, as shown in Figs. at, 5, 6, 7, S and 9, are arranged obliquely on the periphery of said wheel. Secured to the side of said impulse wheel and insulated therefrom is also a rotary impulse tooth H. the radial edges of which are bent outwardly, as shown in Figs. 4, 5, 6, 7, S and S). Said teeth are used for suceessively operating the impulse springs. The ratchet i1 is provided with a suitable coiled spring which normally retains the said ratchet in engagement with the ratchetwheel 37. Said ratchet is so designed. that when the dial is rotated in a eounterclockwise direction (when viewed from the rear, as in Fig. 1), the ratchet 4:1. does not lock with the ratchet-wheel, but upon returning in a clockwise direction (viewed from the rear) the ratchet is drawn closer into engagen'ient with the ratchet-wheel 37, whereby the speed of backward rotation of the dial is controlled by the governor 40.

The prong 32 of the switch-hook member I), in addition to the ratchet 35, carries pivotally secured thereto a link member 46, the outer end of which link is curved and adapted to engage a retracting spring 4L7, which causes a downward swing of the switchhook about the pivots 33 when the receiver is removed. Said spring 47, as shown, is held in position by the brace 48 and the tierod 3. The impulse springs 19 and 50 (Fig. 3)the former being known as the vertical impulse spring and the latter as the rotary impulse springare mounted on the back keyboard plate 2, but suitably insulated from each other and from the said plate.

The vertical impulse spring 49 is provided with an oblique projection or lug 51 on the under side with which the vertical impulse teeth 43 are adapted to engage for driving the spring 49 intermittently onto the ground post 19. The rotary impulse spring 50 is provided with somewhat similar mechanism for driving the said rotary spring onto the ground post once when the dial is rotated in one direction and once when rotated in the means.

'53 which works in conjunction with said V- shaped member; As shown more clearly in Fig. 3-, the auxiliary spring 53 is provided with a lower curved part 6 having the rear section 54: curving outwardly, as shown also iii-Figs. 4, 5, 6, 7, S and 9. The front section of said member 6 is designed to fall just below the apex of the V-shaped' member 52, so that the rotary impulse tooth 44, when moved in the direction of the arrow (Fig. i), will pass onto the curved member 6, thus pressing the rotary impulse spring 50 onto pulse-wheel continues to advance in the dirertion oi the arrow (Fig. 6) the next impulsc tooth will clear the projection 51, as shown in Fig. 7. Then when the impulsewheel is released, the vertical impulse spring it) is twice carried into engagement-with the ground post 19, in the manner indicated in Fig. 8; but as the impulse-wheel nears its normal position the rotary impulse'tooth 44: passes under the curved member 6 of the auxiliary spring 53 (Fig. 9), engaging the V shaped member 52 directly and for a short time only, sending the ordinary impulse through the medium of the rotary impulse spring 50 tothe line, after which the said member 52 is cleared, as shown in Fig. 4, as the impulse-wheel reaches its normal position. The operations as thus described are repeated each time that the dial is operated, and the number of impulses produced through the medium of the vertical impulse spring 49 being accurately and definitely determined at each operation of the dial by the finger-hole which the subscriber selects on the dial 6. It should be stated that a suitable stop is, of course, provided, as is well known in the art, to always limit the rotation of the dial, which stop indicates to the subscriber when he should release the dial. By referring to Fig. 10 it will be noticed that the impulse springs 49 and 50 are electrically connected with the vertical and rotary line conductors-56 and 57 that lead to the central oiiice. The impulses may be used for operating any desirable switching apparatus. It will further be noticed that the ground spring 18, which is controlled by the cam linger l3 and by the locking cam 9, is connected directlyto the substation ground G I scribers line.

which is, of course, connected with one of the terminals of the central oflice battery B, the other terminal of which battery is connected through suitable relays or coils with the line conductors 56 and 57.

Referring to Fig. 10 it will be seen that when the switch-hook is down the ringer 58 is bridged across the line, since the springs 27 and 28 are kept in electrical connection bythe arm 23 and conductor 23. It will also be observed that the transmitter circuit is normally open, since the springs 29 and 30 are kept apart by the arm, 23. Vhen the switch-hook goes up the ringer 58 is, of course, disconnected from the line, and the receiver 10 is connected across the line in series with the secondary winding 62 of the induction coil (31, the primary winding 60 of which is connected in a local circuit with the transmitter 59. Since the release spring 24 is connected with the ground post 19, after the dial has been operated the pressing together of the springs 24, 25 and 26 will ground the Erickson and Erickson, are used, and in which connectors of the general type disclosed in United States Patent No. 815,176. issued March 13, 1906, to Keith, Erickson andlErickson, are used. Such an exchange is outlined in Fig. 11 where (1 represents the said selector switch and E the said connector switch. The subscribers tation is shown terminating in .a switch A individual to the line and ordinarily known'as a line switch. lVith the arrangement shown, there will, of course, be one line switch to each sub- The selectors, however, as well as the connectors, are'less in number than the individual switches, and any percentage basis may be used. For example,

and as is very commonly the case in exchanges, to every one hundred lines there will be provided, in addition to the regular line switches, about ten selectors and about ten connectors. In a one thousand line exchange, for example, there will be one thousand line switches and one hundred firstselectors and one hundred connectors, the connectors, of course, being arranged in groups, one for each hundred subscribers; all subscribers lines of a certain hundred terminating, of course, in multiple bank contacts of the connectors of that particular group, as 'is well known. Should the en:- change be equipped for a greater number of subscribers, then it becomes necessary, of course, to interpose other selectorsbetween the first-selectors and the connectors. lit

.95 No. 815,321, issued March 13, 1906, to Keith,

may be desirable to further insert selectors between the said last-named selectors and the connectors, said selectors being usually known as second-selectors and third-selectors. As shown in Fig. 11, the calling subscriber employs only an individual switch, a first-selector and a connector in obtaining-the desired connection with the called subscribers line. In any event, how-.

. by the back rotation of the dial after it is released by the calling subscriber.

In Fig. 11 the subscribers individual switch A is of the gene a] type disclosed in application Serial No. 311,327, filed April 12, 1906, in which application the individual switch is operated by a rotary impulse transmitted over the rotary side of the line by the switch-hook. It has also been proposed, in a system employing a separate impulse-transmitting key for each side of the subscribers line, to employ the key on the rotary side of the line for transmitting a preliminary impulse over the rotary line conductor to operate the individual switch. it will be seen, however, that I am the first to provide an operative arrangement by which the individual switch is operated by an impulse transmitted over the so-called rotary side of the line when the dial is given its initial or forward rotation. Among other things I am the first to provide a dial with mechanism which will transmit a relatively long impulse upon the forward rotation thereof and a relatively short impulse over the same side of the line upon the back or return rotation of the same. Such relatively long impulse transmittedhy the forward rotation of the dial tends to insure the proper operation of the individual switch. For the final rotary impulse transmitted by the final return or restoring movement of the dial, a comparatively short closing of the grounded circuit is sutiicieut, inasmuch as the subscriber releases the dial and allows it to return of its ()Wll accord to normal position. In operating the individual switch. however. the calling subscriber might rotate the dial very quickly. and inssuch case a short contact arrangement might not be sufficient. and the switch would then fail to operate. Consequently, with my improved arrangement by which a su'tficient closing of the grounded circuit is insured upon the forward rotation of the dial, even though the rotating of the dial be done quickly, the proper responsive action of the individual switch is insured.

The back rotation of the dial is governed or controlled,- so that in this case only a comparatively short or momentary contact arrangement is necessary in order to insure the proper energizing of the rotary line relays of the selectors and connectors. For example, in Fig. '11 of the drawings the trunk line B connects the individual switch with the selector C, and a second trunk line D leads from the said selector to the connector E. As previously stated, this connector will not respond to the forward rotation of the dial, when the latter is operated for the last two digits of the called number. The socalled rotary relay and private magnet of the connector will be energized by such forward rotation of the dial. lnasmuch as the mechanism of the connector side switch is at such time locked in first position, such encrgizing of the private magnet will not release the side switch and will not produce any undesirable results. After the connector has been operated by the-so-called vertical impulses transmitted by the back rotation of the dial, the said private magnet is, of course, then in condition to respond operatively to the single so-callcd rotary impulse transmitted by the final restoring movement of the dial, permitting the side switch to shift to second position. The next forward rotation of the dial will not operate the connector side switch, because the latter is then locked in second position by the cam on the shaft of the connector. The dial when released for the last time will then accomplish the final operations of the connector in the usual manner. As the said connectors as well as the selectors are well known and understood, it will not be necessary to describe them in detail. vlt may be stated, however, that when second and third selectors are employed they do not operatively respond to the forward rotation of the calling dials, for substantially the same reason that the connectors do not operatively respond to such forward rotation. As shown, the system is operated on the local battery plan, but it will be understood, of course, that common battery connectors and subscribers telephones can be employed if necessary or desirable. It will also be understood that in the drawings the calling dial mechanism is shown reversedthat is to say, in such manner that it is viewed from the back. ()rdinarily, however, the subscribers switch-hook projects to the left, so that the finger-holes in the calling dial are in position to be engaged by the right hand of the calling subscriber.

With an elongated or prolonged prelimititans v a a nary impulse, such as the one transmitted by the forward rotation of the subscribers calling dial, the ground circuit isliable to remain closed after the individual switch is operated, and such preliminary impulse then has access to the next switch, such, for

example, asthe first-selector. For reasons already explained, however, the first-selector cannot operatively respond to such preliminary impulse over the rotary side of the line circuit, because its side switch is locked in first position.-

The km or individual switch, as shown in Fig. 12, is. built about a metallic base or frame 63, and comprises a plunger 64k and plunger-arm 65. It is also equipped with a bridge-cut-ofl relay 66, a trip magnet 67 and switch release magnet 68. A section of the metal from the central portion of the frame is removed to make the structure as light as possible, while another section of the portion is turned up at right angles to the base of the frame to form a lug or flange 69 upon which the said switch release magnet is mounted. Said flange has stamped through it a couple of circular holes through which the ends of the cores 70 are passed to main tain the coils of the said release magnet parallel with the base of the frame. They are retained in this position by a U-shaped looking collar 71, between the faces of which the magnet supporting flange 69 extends, and

- which collar has four openings, two on each of the parallel faces, arranged to form two tandem sets through which the cores 70 of the switch release magnet pass, as shown. After the coils of the magnet are inserted in position, the cores are then tightened in place by a' shearing action produced upon the said cores of the switch release magnet between the flange and the capping collar by means of a screw 72 that passes throu h.

a threaded portion on the said collar, t e

end of which screw is forced onto the upper edge of the magnet-supporting flange .69. The said switch release magnet is provided with an'armature 73 that is pivoted on a pin 74 which rises from the base of the switch. The said armature carries, pivotally secured on its end, a second armature 75 that is controlled by the trip magnet 67. The pin 76 about which the armature 75 oscillates is carried on the end of the armature 73. The plunger 64 is pivotally secured by the pin 77 to the plunger arm 65, which latter is in turn pivoted to a pin 78 that rises from the switch frame 63. The lug 79 is stamped out of the frame 63 and is provided as a stop or rest for the armature 73. The trip magnet 67 is mounted upon the frame 63 in the same manner as the release magnet '68. Upon the armature is secured the catch 80 which is adapted to engage the end 81 of the plunger arm 65. I

The general operation of the switch is as o lows: The trip magnet 67 is energised by the preliminary mpulse and the armature 75 s at racted g inst the magnet cores- When the armature 75 is attracted to the left (Fig. 12) the catch 80 lides out of contact with the end 81 of the plunger arm 65, and the said plunger arm 65, due to the tension of the spring 82, moves about the pin 78 and thrusts th plunger 64: into the bank terminal J. When the trip magnet a ain de nergizes, the trip armature. 7.5 alls against the 6nd of the plunger arm 65,, but out of engagementtherewith. The switch is es red, hen th release magnet 68 be.- comes energized, whereby he armature 73 i attracted,'and accordingly the connected rip arm re 7. is moved upwardly until the catfih 80 passes over the end .81; then when the release magnet 68 becomes oleenergized the armature 73 returns to normal position, at rest against the Stop 79. Finthermpre, since t p nger arm 65 is new he master switch, which is shown (lifts grammatically below the individual switch A and the fi s -se ector C, may be of any suitable or approved type, and'is provided for operating the plunger shaft 83 and for controlling certain circuits that will he disclosed hereinafter......aaid master switch comprises, among other details, a motor magnet 84: for operating the ratchet-wheel 85, said ratchetwheel being provided with a number of pins 90, 91, 92 and 93 phrough the medium of which, and by the codperation of the cam 89, the plunger shaft 83 is operated. It Will be noticedthat rigidly connected it) the said cam 89; there is a master switch wiper 88 which is maintained in contact with the master switch bank 0. Said master switch bank 0 comprises a set of contacts it arranged along the arc of a circle and a common member 87. The arrangement is such that the wiper 88 is adapted to mainta'inat all times some one of the contacts it in else-- tions of the individual switch plunger 64;.

It may be assumed that when the individual switch plunger 64 is in the first position it is opposite the said springs shown in Fig. 12. Of course, when the plunger passes to second position it will be carried opposite a similar and adjacent set, and when it passes to third position will be opposite a third set, etc. The arrangement in this systemis such that" when the master switch wiper 88 is in first positionthat is, when the master switch wiper 88 is onthe contact point 97- the individual switch plunger 64 is'then retained by the plunger shaft 83 opposite the first set of bank springs 111, 112, 113, 114, 115, 116, 117 and 118; and when the motor magnet 84 energizes and advances the ratchet wheel 85 one step, the pin 90, through the medium of the cam 89, advances the master switch wiper 88 onto the second master switch bank contact 102, and at the same time it advances all idle individual switch plungers opposite the second set of individual bank springs, and so on for ten successive steps of the ratchet wheel 85.

' After the wiper has been carried onto the tenth contact, then when the motor magnet energizes again the pin '90 on the ratchet wheel 85 nears the end of the cam 89, and the retracting spring 96 restores the master switch wiper 88 and the plunger shaft 83 to the first position. At'each'position it is brought to a standstill by the engagement of the cam 89 with the succeeding pin 91. It will be seen, therefore, that the continued operation of the motor magnet 84 produces an oscillatory movement of the master switch bank wiper and of the plunger shaft 83. In addition, the master switch is provided with a difierential relay 86 comprising two windings, which windings are in opposition across the terminals of the battery B. allotted to its control a couple of springs 100 and 101 comprising the energizing circuit of the motor magnet 84, and whenever said differential relay energizes, the said springs 100 and 101 are carried into contact for operating the said motor magnet. The master switch has, in addition, an auxiliary relay 119 for controlling the energizing circuits of all trip magnets 67 of the individual switches controlled by the master switch. The said relay is included in the circuit that extends between the common segment 87 of the master switch bank 0 and the and not through the bridge-cut-off relay springs, as shown in the said patent. Therefore, the bridge-cut-ofi relay springs and the bridge-cut-olf relay are dispensed with. Furthermore, the vertical, rotary and pri- The said differential relay has 1 vate normal conductors are disconnected from the selector and are allotted to the individual switch A. In the drawings (Fig. 11) the mechanism of the switches is not shown, but the circuits are outlined, which circuits comprise and are controlled by the line relays 103 and 10-1, the vertical mag- .net 122 for raising the shaft, the private shaft wipers are indicated at 128, 129 and The connector E is of the general type disclosed in said United States Patent No. 815,176, and, as is well known, comprises the line relays 112 and 113, the vertical magnet 129, the rotary magnet 130,- the private magnet 131, the release magnet 132, the vertical back-bridge relay 133 and the rotary back-bridge relay 134, and the ringer relay 135. Of course, the said vertical magnet controls the vertical operation of the switch-shaft that carries the line and private wipers 136,137 and 138. The rotary magnet 130 controls the rotation of the switch-shaft. The private magnet 131 controls the side switch; the ringer relay 135 controls the signaling, and the release magnet 132 controls the releasing of the switch. The back-bridge relays 133 and 131 comprise means under the control of the called subscriber for releasing the connector if he should so desire. The side switch, as shown, comprises the side switch wipers 13$), 14.0, 14.1 and 142.

As shown in Fig. 11, suppose that the subscriber at substation #500 desires to call the substation #220; then when the dial is given its first forward rotation the rotary impulse tooth 14 engages the rotary impulse spring 50, as previously explained; and as shown in Fig. 5, preliminary ground impulse is sent over the rotary line conductor 57, whereby the trip'magnet 67 of the line switch A becomes energized over the following path: from ground G through the coiiperating ground springs 18 and 19, rotary impulse spring 50 to the rotary line conductor 57, bridge-cut-oif springs 108 and 109 through the winding of the trip magnet 67, springs 11.0 and 111 of the master switch relay to the battery lead 105, thence through battery B and to ground G. The trip magnet 67 upon energizing attracts its armature 75, thus drawing the catch 80 from the terminal 81 of the plunger arm itself, whereby the plunger 61 by the force biddat l of the spring 82 is thrust onto the plunger bank terminal J, assuming that the plunger is in firstposition. When the plunger enters the bank the springs 111 and 114 are carried into contact, and the springs 115 and 118 are carried into contact, whereby the subscribers line conductors 56 and 57 are extended to the trunk conductors B which lead to the first-selector C. Furthermore, the springs 116 and 117 are carried into contact, and the release magnet 68 of the individual switch A is placed in connection with the third or trunk-release conductor 1 13 that terminates in the release relay spring 1414: at the selector C, controlled by the release relay 126. Furthermore, the bank springs 112 and 113 are carried into contact, whereby the guarding potential is established at the connector bank contactsof the calling line, and whereby the circuit is established through a cutofi' relay 66 for disconnecting the trip magnet 67 from the rotary line conductor 5 7. The first digit being 2, the grounding of the vertical and rotary line conductors 56 and 57, y

when the calling subscriber operates his dial, energizes the vertical androtary line relays 103 and 104 of the first-selector C, whereby the said selector operates, as is well known, to extend the conductors leading to it to the trunk conductors D, which latter in this case lead to the connector E.

The grounding of the line conductors 56 and 57 for the last two digits has the result of operating the connector E to establish connection with the line #220. If the said line is not busy the said operations are performed through the medium of the vertical and rotary line relays 112 and 113 After the central ofiice switches have been operated, as described, they may be restored to normal condition by the calling subscriber upon hanging up his receiver, at which time,

as is well known, the vertical and rotary line conductors 56 and 57 are, of course, simultaneously grounded, when the release springs 21, 25 and 26 are pressed into contact. 'Of course, the line relays 112 and 113 are energized simultaneously, at which time the trunk-release springs 110 and 141' are carried into engagement, and the trunkrelease circuit is established that comprises the release magnet 132 of the connector E;

released until the substation ground is broken, when the release springs 24, 25 and 1. In a telephone exchangev system, the

combination of a subscribers rotatable call- .ingdial, an impulse-transmitting mecha nism governed thereby, an automatic switch responsive to the operation of said mechanism by the forward rotation of said dial, when rotated for the first digit, another switch responsive to the operation of said mechanism by the return or backward rota tion of the dial, a third switch responsive to the backward rotation of the dial when rotated for the second digit, and means for preventing said third switch from operatively responding to the forward rotation of the dial.

2. In a telephone exchange system, the combination of a subscribers rotatable calling dial, a subscribers individual'switch, a first-selector switch, a subscribers telephone line, means by which the forward rotation of the dial transmits an electrical impulse over one side of the line to operate the said individual switch, and means by which the backward rotation of the dial transmits one or more electrical impulses over the line to both initially and finally operate the selector-switch.

3. In a telephone exchange system, the

combination of a subscribers calling dial, a

subscribers telephone line provided with socalled rotary and vertical line conductors, a subscribers individual switch, another switch having vertical and rotary motion controlled over said line conductors, and means by which the forward rotation of the dial transmits a preliminary electrical im pulse over the rotary side of said line to operate the said individual switch.

1. In a telephone exchange system, the combination of a subscribers calling dial, a subscribers telephone line, means by which the forward rotation of the dial transmits an electrical impulse over one side of said line,iand means by which the backward rotation of said dial transmits electrical impulses over both sides of said line, together with switching apparatus operatively affected by said impulses.

5. In a teleahonc exchangesystem, the combination of a subscribers rotatable calling dial, a subscribers telephone line, means by which the forward rotation of the dial, when rotated for the first digit, transmits a relatively long electrical impulse over one side of the line, and means by which the backward rotation of the dial transmits one or more electrical impulses of shorter duration over the other side of the line, followed by an impulse over the first side of the line, together with switching apparatus operatively affected by said impulses.

25 separate, at which time the central office v "6. In a telephone exchange system, the

combination of a subscribersrotatable dial, a subscribers telephone line, means for grounding the so-called rotary side of the tion of the dial, and means for grounding the so-called vertical side of the line upon line upon both the forward and back rotathe backward rotationof the dial, together grounding of the line.

ward and backward rotation of the dial, and

:means by which the other side of the line is grounded upon the back rotation of the dial,

together with automatic switching means responsive to such grounding of the line.

8. In a telephone exchange system, the combination of a subscribers movable calling device, a subscribers telephone line, means by which the forward movement of said device operates'to ground one side of the line, means by which the return or backward rotation of the dial operates to ground both sides of the'line, one side at a time, together with automatic switches responsive to such grounding of the line.

' 9. In a telephone system, a subscribers line, a non-numerical trunking switch individual thereto, a connector for finding the called line, means including a selector for trunking the individual switch into connection with the said connector, a subscribers calling mechanism provided with a rotary dial, means whereby. the forward rotation of said dial operates the said non-numerical individual switch, and means whereby the backward rotation of the dial is operative to control the selector andthe connector.

10. In a telephone system, a connector having one motion to select groups and another motion to find the called line in any selected group, means including a subscribers non-numerical individual trunking switch for extending connection to said connector, a subscribers -calling mechanism provided with a rotary dial, means whereby the said non-numerical switch is responsive to the forward rotation of said dial, and means whereby the said connector is responsive to the backward rotation of said dial.

12. In a telephone system, the combination of a subscribers rotary calling dial, a

subscribers telephone line, means by which the. initial forward rotation of said dial transmits a relatively long electrical impulse over one side of the line, means by which the backward rotation of the dial 7 transmits one or more electrical impulses of nism by the forward motion of said dial,

when operated for the first digit, another switch responsive to the operation of said meehanismby the return or backward. motion of the dial, a third switch res onsive to the backward motion of the dia when operated for the second digit, and a latch for preventing said third switch from operatively responding the forward rotation of the dial.

14. In a telephone exchange system, the combination of a subscribers reciprocating calling dial, a subscribers individual switch, a first-selector switch, a subscribers telephone line, an impulse sender controlled by the dial by which the forward rotation of the dial transmits an electrical impulse over one side of the line to operate the said individual switch, and by which the backward rotation of the dial transmits one or more electrical impulses over the line to both initially and finally operate the selector switch.

15. In a telephone exchange system, the combination of a subscribers calling dial, a subscribers telephone line provided with socalled, rotary and vertical line conductors, a subscribers individual switch, another switch having vertical and rotary motion controlled over said line conductors, and an impulse sender controlled by the dial b which the forward rotation of the dia transmits a preliminary electrical impulse over the rotary side of said line to operate the said individual switch.

16. In a telephone exchange system, the combination of a subscribers calling dial, a subscribers telephone line, an impulse sender controlled by the dial by which the forward rotation of the dial transmits an electrical impulse over one side of said line, and by which the backward rotation of said dial transmits electrical impulses over both sides of said line, together with switchmg apparatus operatively affected by said impulses.

17. In a telephone exchange system, the

1,133,373 ital combination of a subscribers rotatable calling dial, a subscribers telephone line, an impulse sender controlled by the dial by which the forward rotation of the dial when rotated for the first digit, transmits a relatively long electrical impulse over one side of the line, and means by which the back- Ward rotation of the dial transmits one or more electrical impulses of shorter duration over the other side of the line, followed by an impulse over the first side of the line, together with switching apparatus operatively affected by said impulses.

18. In a telephone exchange system, the combination of a subscribers rotatable dial, a subscribers telephone line, an impulse sender controlled by the dial for grounding the so-called rotary side of the line upon both the forward and back rotation .of the dial, and for grounding the so-called vertical side of the line upon the backward rotation of the dial, together with automatic switches responsive to such grounding of the line.

19. A telephone exchange system cornprising a subscribers rotatable dial, a subscribers telephone line, an impulse sender controlled by the dial by which one side of the line is grounded on both the forward and backward rotation of the dial, and by which the other side of the line is grounded upon the back rotation of the dial, together with automatic switching means responsive to such grounding of the line.

- 20. In-a telephone exchange system, the combination of a subscribers movable calling device, a subscriber's telephone line, an impulse sender controlled by the dial by which the forward movement of said device operates to ground one side of the line, and by which the return or backward rotation of the dial operates to ground both sides of the line, one side at a time, together with automatic switches responsive to such grounding of the line.

21. In a telephone system, a subscribers line, a non-numerical trunking switch individual thereto, a connector for finding the called line, a progressively movable trunking switch for trunking the individual switch into connection with the said connector, a subscribers calling mechanism provided with a rotary dial, an impulse sender controlled by the dial which upon the forward rotation of said dial.operates the said nonnumerical individual switch, and which upon the backward rotation of the dial is operative to control the selector and the connector.

22. In a telephone system, a connector having one motion to select groups and another motion to find the called line in any selected group, a subscribers non-numerical individual trunking switch for extending connection to said connector, a subscribers calling mechanism provided with a rotary dial, an impulse sender controlled by the dial, said non-numerical switch responsive to said sender upon the forward rotation of said dial, and the said connector is responsive also to said sender upon the backward rotation of the dial.

In a telephone system, an automatic numerical trunking switch having one motion to select groups and another motion to automatically find an idle trunk in any selected group, a non-numerical trunking switch, a calling mechanism provided with a rotary dial, an impulse sender controlled by the dial, said non-numerical trunking switch responsive to the sender upon the forward rotation 'of said dial, the said numerical switch also responsive to the sender upon the backward rotation of said dial.

524. In a telephone system, the combination of a subscribers reciprocating calling dial, a subscribers telephone line, an impulse sender controlled by the dial through the medium of which said dial transmits a relatively long electrical impulse over one side of the line upon forward motion and through the medium of which the dial transmits one or more electrical impulses of shorter duration over the other side of the line upon backward motion, followed by a single impulse over the first-mentioned side of the line of short duration, and switching apparatus controlled by said impulses.

Signed by me at Chicago, Cook county, Illinois, this 7th day of November, 1906.

JOHN ERICKSON.

Witnesses Bowman D. FALEs, CHARLES J. ERICKSON. 

